The embodiments described herein relate generally to a security screening system and, more particularly, to a multi-stage security screening system with a smart communication system between the stages.
Many known security systems for screening containers for materials and item of interest include a two-stage screening system. As used herein, the terms “materials of interest” and “items of interest” refer to contraband substances such as, without limitation, explosives, narcotics, and weapons that may compose a threat in an inspected region of the containers. Also, as used herein, the term “containers” refers to, without limitation, luggage, shipping packages and parcels, bags, cargo, and vehicles.
The first stage is typically a pre-screening stage that uses X-ray devices such as a transmission pre-screener, e.g., single-view devices, advanced technology multi-view devices, and computed tomography (CT) systems. Such pre-screening is typically performed at cabin baggage screening (CBS) checkpoints and/or hold baggage screening (HBS) checkpoints. Also, while such pre-screening devices facilitate determining a density of the objects in the container, including relative densities of such objects, and the approximate coordinates of the objects within the container using the spatial resolution properties of such pre-screening devices, they are not molecular-specific. Therefore, a second stage is typically used downstream of the pre-screening stage. The second stage is a screening stage that uses X-ray diffraction imaging (XDI) devices to resolve alarms raised by the x-ray pre-screener. The molecular-specific detection performance of the XDI device enables it to accurately resolve alarms raised by the transmission pre-screener. Such XDI devices generate a diffraction profile of each substance irradiated with X-rays. Because such materials typically have a known and discernible X-ray diffraction (XRD) signature, detection and identification of contraband items and substances is facilitated.
Such pre-screening stage transmission X-ray systems have a tendency to increase the false alarm rate (FAR). Also, such pre-screening stages transfer only approximate threat coordinates and the nature of the supposed threat via a simple communication stage to the subsequent XDI scanner. Therefore, the irradiating power of the X-ray scan by the XDI device must be increased and the scan period extended to accurately resolve the alarms. Such increases in the scan period and power usage increase the costs of screening. Also, since the communications between the pre-screening stage and the XDI scanner are one-way only, there is no feedback mechanism to calibrate the pre-screening stage to improve alarm accuracy and decrease the FAR.